Thermomechanical Pulp Fiber Surface Modification for Enhancing the Interfacial Adhesion with Polypropylene

Chemical coupling on the thermomechanical pulp (TMP) fiber improved tensile strength of the TMP fiber handsheet and isotactic polypropylene film laminates (TPL). For the maleic anhydride (MA) with benzoyl peroxide (BPO) as an initiator, tensile strength increased 52% with the TMP fiber treatment over untreated laminates. The optimum strength properties were obtained with an MA and BPO ratio of 2:1. Scanning electron microscopy (SEM) images also showed the effectiveness of MA loading on the surface of TMP fibers due to increased fiber failure without fiber pullout from the polypropylene matrixes. Crystallinity and heat flow from DSC, as expected, decreased with the addition of MA on the TMP fiber surface. These results were also in accordance with the morphological observations at the fracture surface, Fourier-transform infrared spectroscopy (FTIR) spectra, and thermal analysis. Based on the high correlation between tensile strength and the number of fibers counted at the point of failures, the number of fibers proved to be a sensitive measure of the effectiveness of surface treatment